1. Field of the Invention
This invention relates to an improved method of preparing trinitrophloroglucinol.
2. Description of the Prior Art
Many aromatic compounds with nitro groups on the rings are useful explosives. Trinitrophloroglucinol can serve as an explosive, but this use has been limited by the lack of a safe, simple, and inexpensive method of production. Salts of trinitrophloroglucinol are useful as initiators. Additionally, trinitrophloroglucinol serves as an important intermediate in the synthesis of several other explosives.
Previously, trinitrophloroglucinol has been obtained in a variety of ways. Typical procedures include the alkaline hydrolysis of precursors such as pentanitroaniline (B. Fl/u/ rscheim et al., J. Chem. Soc., 3044, 1928) or 1,3,5-trichloro-2,4,6-trinitrobenzene (F. Sorm et al., Chem. Obzor., 12, 153, 1937; Chem. Zentralblatt, II, 4033, 1937). Another procedure involving nitrolysis of the tripotassium salt of trinitrosophloroglucinol is quite hazardous (K. Freudenberg et al., Ann. 442, 309, 1925). Other methods begin with phloroglucinol and involve the nitrosation of the phenol, followed by subsequent oxidation with nitric acid to give the trinitrophloroglucinol as shown in Ger. Pat. No. 1,959,930 or the two-step nitration of Russ. Pat. No. 515,740 which nitrated the phloroglucinol to give them mononitro phloroglucinol, followed by a second nitration to give the trinitrophloroglucinol.
All the earlier procedures suffer from limitations including use of a multi-step synthesis, a poor overall yield, or the hazards of preparing very sensitive, highly explosive intermediates during preparation of trinitrophloroglucinol. An alternative process is desirable to allow the improved production of trinitrophloroglucinol.
The novel process of this invention concerns the direct nitration of phloroglucinol and provides a simple, inexpensive and efficient one-pot synthetic route to trinitrophloroglucinol.
Huntress and Mulliken previously reported an undetailed description of the nitration of phloroglucinol to obtain trinitrophloroglucinol in "Identification of Pure Organic Compounds," p. 248, John Wiley and Sons, Inc., New York (1941). This method consisted of adding a solution of 0.1 g of phloroglucinol in concentrated H.sub.2 SO.sub.4 into a mixture of 1 ml each concentrated H.sub.2 SO.sub.4 and concentrated HNO.sub.3. However, the authors of this specification were unable to duplicate the earlier results. Using that procedure, scale up to even 1 g of phloroglucinol was unsuccessful and no product could be isolated. Accordingly, the hereinafter disclosed method of preparing trinitrophloroglucinol was developed after considerable experimentation.